Scenario

A 21 year-old heavy-set female with no prior medical history presents to your emergency department complaining of dull intermittent frontal headaches for the past 3 months. These headaches have no identified triggers, aggravators, or alleviators. They occur about three times daily, irrespective of position or time of day. They are associated with occasional nausea and transient binocular vision loss. She denies fever/chills, chest pain/shortness of breath, diarrhea, syncope, weakness. She has taken Ibuprofen 400 mg for these headaches but the medicine is bringing her less relief as time goes on. No other family members at home have had similar headaches.

Vital signs are within normal limits.

On exam, the patient is very well appearing without any visual deficits or other neurological findings.

The resident does not believe that this patient’s headache constitutes one of the acute dangerous headaches that must be ruled out immediately in the ED. Even if the resident had ordered a CT scan, he/she would have found it to be normal. In all likelihood, these headaches simply represent migraines that are not responding to Motrin anymore. That being said, the resident tells the attending, could these headaches possibly represent pseudotumor cerebri… or benign intracranial hypertension… or idiopathic intracranial hypertension…or whatever they are calling it these days? Should he/she perform an LP and go down that path?

Type of Study: single-center, prospective, rater-blindedObjective: to determine whether bedside OUS could identify elevated intracranial hypertension in patients aged 12-18 suspected of having idiopathic intracranial hypertensionResults: 13 patients in study, 10 of whom had elevated intracranial pressure. ONSD was able to predict or rule it out in all 13 patients.Conclusion: Non-invasive assessment of ONSD could help identify patients with elevated intracranial pressure when idiopathic intracranial hypertension is suspected

Measure the optic nerve sheath diameter at a distance 3 mm posterior to the globe, where the US contrast is greatest.

http://sinaiem.us/education/papilledema-and-the-crescent-sign

Measure the ONSD twice. Determine the average.

An ONSD > 5 mm suggests elevated intracranial pressure.

The optic nerve sheath contains fluid in which sits the optic nerve. The sheath attaches to the posterior aspect of the globe and is contiguous with the subarachnoid space. Accordingly, the ONSD can act as a surrogate for intracranial pressure.

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